Lorentz Center - New computational methods in Quantum many-body theory from 10 Aug 2009 through 14 Aug 2009
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    New computational methods in Quantum many-body theory
    from 10 Aug 2009 through 14 Aug 2009

Scientific Report

Scientific Report


New Computational Methods in Many-Body Theory

August 10-14, 2009


Scientific Background: the last few years have seen extraordinary advances in the numerical solution of the equations of interacting particle quantum mechanics.  In particular, new developments in continuous-time Quantum Monte Carlo (CT-QMC) and density matrix renormalization group (DMRG) methods have made it possible to obtain comprehensive, numerically exact solutions to some of the basic model systems of quantum condensed matter physics.  These successes have revolutionized quantum many-body physics, opening a broad spectrum of  problems including simulations of magnetic nanosystems on metallic surfaces,  the Mott transition in multiorbital systems, the Hubbard-Holstein problem, and can be combined with traditional electronic structure methods to study previously inaccessible compounds such as plutonium, heavy-fermion systems, strongly correlated thermoelectric compounds and novel high-temperature superconducting pnictides as well as to the fundamental question of the nonequilibrium properties of nanosystems and solids.


Workshop: These successes make it highly desirable and timely to gather together the inventors and practitioners of the new techniques, to consolidate the success, identify the open problems and formulate the next steps in the field. Equally important is to involve experimentalists (to identify the important open physics problems which the theoretical community could tackle) and practitions of other areas of electronic structure and many-body physics, for cross-fertilization of ideas and a wider perspective on the theoretical issues.   The Lorentz Center workshop “ New Methods in Quantum Many-Body Theory” was held in response to this need. It featured 41 scientists who gathered for a program of 3 seminars per day—one by an experimentalist and two by theorists. We also had two formal discussion sessions as well as many lively discussions in and out of the seminar room. 


The participating scientists were a mix of “numerical correlated electron” specialists who have devised and are now using the new techniques, theorists from the wider field of electronic structure and quantum chemistry, and experimentalists. Talks presented recent achievements made possible by the new methods and led to discussions which clarified the relative strengths of the different methods. A crucial issue for the field is that the new developments pertain mainly to the solution of model systems; some of the talks indicated methods for moving beyond model systems towards a quantitative description of real materials


The interactions between people coming from different fields were very useful. Thus, one success of the workshop was the approximately one talk per day from theorists outside of the correlated electrons community. These talks provided valuable insights into the broader classes of problems that should be addressed with the new methods. Another high point was a discussion session which led to a list, formulated by the participating experimentalists, of important frontier physics issues raised by new generations of measurements which could be addressed by the new techniques.  This list will be the basis of a range of planned new work.


While there was a large amount of extremely interesting material to present and the lectures were of high quality, we feel in retrospect that a slightly less heavy program would have been even more beneficial, allowing the participants more time to interact informally.


Mikhail Katsnelson, University of Nijmeigan

Alexander Lichtenstein, Universitat Hamburg

Andrew Millis, Columbia University